Sound apparatus



Oct. 23,1934. Y R. L. WILLIAMS 1,977,663

scum) APPARATUS Filed May 23, 1929 2Sheets-Sheet' l INVENTOR. Robert L.Williau'rzs- ATTORNEY I-. WlLLlAMs SOUND APPARAT Oct, 23, 193

Filed May 23, 1929 2 Sheets-Sheet 2 "(PE/(70k Robert L, Wi .7 9;, i vATTO EY hem d on. 23, 1934 I UNITED STATES SOUND APPARATUS RobertLongfellow Williams, Newton, Masa, as-

slgnor to Submarine Signal Company, Boston, Mass., a corporation ofMaine Application May '23, 1929,'Serlal No. 365,385 3 Claims. (01.177-1) The present invention relates to means for creating sound wavesin any medium, but more particularly in air.

Therev aremany types of sound generators.

.5 For fog or bad weather signaling, it has been common practice to useair sirens, steam or air whistles. Anewertype of sound producer for fogsignaling is the electromagnetic and-electrodynamic type, sometimescalled air oscillators.

These air oscillators are usually designed to produce a sound of a puretone and are found to carry further distances on account of the purenote which they produce. This'is due, it is believed, to the fact thatin the propagation of a pure tone, the ,phases do not become mixed, sothat there is less wattless energy oscillating back and forth inthe-medium. Besides this, the ear very readily detects a pure tone, eventhough it is weak, because of its accumulative effect in building up asubstantial vibration.

It is desirable, therefore, to have a pure tone, and for that reason theair oscillators have been given a definite oscillating resonantfrequency and have been operated at that resonant frequency.

' Air oscillators are operated by alternating current sources deliveringpower at the frequency at which the sound is to,be generated. While thegenerators remain at the frequency at which the sound is to be produced,the maximum en- 30 er'gymaybe drawn from the electric system, but

when the frequency of the electric system fails consequently its rangeof audibility may be affected. This difliculty may be overcome either byhaving a system which'has no particular resonance or by having a systemin which the resonance may be controlled, or by a combination of the twomethods.

Where the system has no marked resonance,'

it has been found difficult in some cases to produce great enoughamplitudes to radiate the power desired with the size of radiatoravailable for use. To overcome this objection without the introductionof a tuned system, I employ a lever arrangement whereby the amplitude ofthe elec- 5 ing element.

trical system is multiplied at the sound radiat- The top of the shell 1is closed by the horn drawings in which Figure 1 shows a section view ofmy invention; Figure 2 shows a modification; I Figure 3 shows a detailof the modification of Figure 2;

Figure 4'shows another detail of Figure 2; Figures 5 and 5a showdetails; and Figure 6 shows a modification of a detail in Figure 1. p

In Figure 1 the electrical system is of the Fessenden oscillator type asshown in the Fessenden Patent 1,167,366. Here the system comprises acore 3, an outer shell 1 composed of two parts bolted together at theflange 5 by bolts 6. Within the shell 1 is a coil 2 in which directcurrent flows to magnetize the air gap between the core 3 and theshell 1. Wound upon the core 3 is a winding 7, through which thealternating current flows for producing alternating current in thecopper or aluminum tube 8. The change of current in the tube 8 causes itto move back and forth longitudinally in the air gap and impart soundvibrations to the sound radiating element. The system shown producesmotion both ways and therefore needs no springs or restoring forces, asin some systems, to bring the oscillating elements back to theirstarting or normal-positions.

The central core 3 is held in position by ears or corners 9, 9, 9, 9 tothe outer shell 1. Mounted on these ears are bearing pieces 10, forkedin shape as shown' in Figure 5a. These pieces support the levers 11 attheir ends by the pins 12 which pass through the levers and the bearingpieces. The levers 11 have their other ends resting in a groove 13 inthe collar piece 14. The levers 11 are spaced radially from. the centralcollar piece 14, as shown in Figure 5, where there 105 are three innumber. There may be more or less, in accordance with the most suitabledesign. The centef collar 14 carries the spider 15, to which theradiating element 16 is attached.

element 17 in the throat of which the radiating piston 16 works. Closingthe edge between the radiating piston and the horn is a disc of rubberor other suitable material 18, clamped to the member 16 and to the wallfor preventing the pressure release to the back of the radiating elementand also to protect the inside mechanism from moisture and bad weather.

At the lower end of the oscillatorare provided similar levers 11 mountedand fastened in the same manner as the levers at the top except thatthere is no radiating member attached to the collar 14. A radiatingmember may be used here, however, if it is desired to radiate from bothends. The copper tube 8, which may be of some other suitable conductingmaterial if desired, has projecting arms 19 which may have knifed edgeends 20 fitting into cuts. in the levers 11 near the pivoted ends, asshown in Figure 1.

When the system is assembled, the various elements are put together andthe nuts 21, 21 at opposite ends of the rod 22 are tightened until thethe desired pressure is exerted between the levers 11 and the arm 19extending from the copper tube. This also tensions the levers 11 againstthe bearing support 12 so that the system is a unified structure.

The tube 8 and the arms 19 have only a small motion, but at the free endoi the levers 11, at

the collar 14, the motion is multiplied in the ratio of the length ofthe lever to the distance between the point of bearing of the arm 19 andthe point of pivot. The center collar has, therefore, an increasedamplitude which is imparted to the radiating element 16 through thespider 15.

The system as shown in Figure 1 has no marked resonance so that ii thefrequency of the alternating current impressed upon the coil 7 shouldchange, due to change in the frequency of the electrical system, assometimes takes place, there will be no appreciable diminution of energyradiated from the device.

If it is. desirable to tune the system tov still further build up theradiation, this may be done by means ofa resonant chamber which has anadjustable volume, as shown in Figure 2. Here the radiating ,element 30forms one wall of the resonant chamber 31. The other wall is formed bythe disclike member 32, threadinginto a ring 33, which is held fast tothe edge 01 the diaphragm member 30 or the casing in a manner which willbe described later.

The horn element is bolted by bolts 35 to the member 32, but the hornand member 32 may be turned on the ring 33, thereby increasing ordecreasing the volume oi'the resonant chamber as may be desired. Whenthe resonant chamber is brought to the volume desired, it may be clampedin place by means 01' the clamping bar 36, held firmly to the ring 33 bymeans of the bolt 37 and lock washer 38, the clampingbar bearing on thedisc 32' as the bolt 37 is tightened.

The horn 34 may be very substantial in weight and give the systemcertain undesirable acousticcoupling. To avoid this, the ring 33 iselasticallycoupled to the diaphragm edge or irame by means oi the bolt40, threading into the frame, which bolt has beneath its head aspring-tensioning element such as a washer 41 dished in the center,

as indicated at 42. This washer bears upon a second washer 43 which isspaced from the ring 33 by means of the spacing member 44. Between theframe and ring 33 is also a gasket 45 of some yielding material, asrubber, canvas, or the like to help damp any vibration which thiscoupling may have.

i This means or acoustically coupling the horn and frame togetherprevents undesired vibrations by damping them immediately.

In place of using a pivoted-lever system, as shown in Figure 1, a systemas shown in Figure 6 may be used, where the levers 50 may have their.ends firmly clamped by means of. the clamping member 51 and bolt 52.The other ends 01 the levers may also be clamped to the rod 32 by meansof the clamping washers 53 and 54 and the'nut 55, threading on the rod22;

Having now described my invention, I claim:

1. Apparatus for producing sound waves ineluding va casing, a diaphragmhaving a heavy rim closing one endoi said casing, a ring positioned onthe heavy rim of the diaphragm, means for securing said ring to saidrim, said ring having an internal threaded side, a plate having anopening positioned opposite the diaphragm on the outer side and forminga chamber in front of said diaphragm, said plate having a threaded edgeengaging the threads on said ring and means for clamping the plate tothe ring, said means being externally positioned on said plate-and ring.

2. Apparatus for producing sound waves including a casing, a diaphragmhaving a heavy rim positioned at one end of said casing, means in saidheavy rim ior clamping the diaphragm to the casing a ring positionedover said heavy rim, means for securing the ring to the rim, said ringhaving an internalthread, a plate having an opening in the center andthreaded at its external edge into said ring-forming a chamber beforethe diaphragm and means for clamping said plate to said-ring.

3. Apparatus for producingv sound waves including a casing, a'diaphragmhaving a heavy rim positioned 'at one end 01' said casing, means forclamping the diaphragm to the casing in said heavy rim, a ringpositioned 'over saidheavy rim,

said ring having an internal thread, a plate having an opening in thecenter and threaded at its external edge into said ring, iormingachamber before the diaphragm, means io'rclamping said plate to said ringandmeansior clamping said ring to said casing. said clamping meansincluding means holding said ring to said casing and spring tensioningmeans positioned 'between said holding meansand said ring.

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